DE102022003747A1 - System for controlling the emission of ammonia released by selective catalytic reduction (SCR) into the atmosphere - Google Patents

Abstract

The present invention discloses a system for controlling the emission of ammonia evolved by selective catalytic reduction (SCR) into the atmosphere, the system (100) comprising an SCR (101) for reducing the amount of NOx emission in the exhaust gas. A pair of ammonia sensors (102a, 102b) detect the presence of ammonia in the exhaust gas downstream of the SCR (101), and an electronically actuated recirculation valve (103) is actuated when the amount of ammonia in the exhaust gas detected by the first ammonia sensor (102a) is is greater than a predefined threshold; Furthermore, a condenser module (104) receives the exhaust gas through the recirculation valve (103) and condenses the exhaust gas at a predefined temperature. A liquid ammonia separator (105) separates the condensed liquid ammonia from the off-gas which is vented to the atmosphere.

Description

In the following description, particular emphasis is placed on the invention and the manner in which it is intended to be carried out.

The present invention discloses a system for controlling the emission of ammonia evolved by selective catalytic reduction (SCR) into the atmosphere ammonia and waste gas is recovered, which is released into the atmosphere.

Currently, vehicle manufacturers use AdBlue to reduce _NOx emissions in the exhaust gases emitted by vehicles.

Selective Catalytic Reduction (SCR), provided in a vehicle's aftertreatment system, chemically reduces _NOx emissions by using ammonia to provide nitrogen, water, and carbon dioxide. However, the exhaust gas downstream of the SCR still contains a predefined amount of ammonia that is released into the atmosphere, which exhaust gas comprising ammonia may be harmful when released into the atmosphere. There is currently no mechanism to reduce the amount of ammonia present in the exhaust before it is released into the atmosphere.

The patent number US6871489B2 entitled "Thermal management of exhaust systems" refers to the thermal management of an integrated emissions reduction system for the removal of particulate matter (PM) and nitrogen oxides (NO _x ) from diesel engine exhaust streams. The inventive integrated emissions reduction system may include a diesel particulate filter (DPF), a heat source for adjusting the temperature of the exhaust stream entering the DPF, at least one selective catalytic NO _x reducer, a heat exchanger for adjusting the temperature of the exhaust stream entering the NO _x reducer, and a Computing device for monitoring the temperature and/or pressure of the exhaust gas stream entering the DPF and the _NOx reducer and for controlling the operation of the heat exchanger and the heat source, thereby improving the efficiency of the DPF and the _NOx reducer.

The patent number US7320781B2 entitled "Method for adjusting a reductant used in an internal combustion engine to reduce NO _x " refers to a method for controlling reductant injection into an exhaust stream upstream of a catalytic converter associated with an internal combustion engine is disclosed. The method uses an ammonia sensor located downstream of the exhaust catalyst to determine the concentration of ammonia in the exhaust stream. The ammonia concentration is compared to an allowable threshold and an allowable fraction, ie a maximum limit for an ammonia fraction in the exhaust stream compared to the ammonia delivered by the reductant injector. Additionally, it is determined based on a _NOx sensor whether the _NOx conversion of the catalyst has increased in response to the increase in reductant injection. If this is not the case, the quantity of reducing agent injected is reduced.

Therefore, there is a need for a mechanism for detecting and reducing the amount of ammonia present in a vehicle's exhaust.

The present invention overcomes the disadvantages of the prior art by disclosing a system for controlling the emission of ammonia evolved by selective catalytic reduction (SCR) into the atmosphere, the system using an SCR for the reduction of the amount of NO _x emission in includes the exhaust gas. A pair of ammonia sensors detect the presence of ammonia in the exhaust gas downstream of the SCR, with an electronically actuated recirculation valve being actuated when the amount of ammonia in the exhaust gas detected by the first ammonia sensor is greater than a predefined threshold. Further, a condenser module receives the exhaust gas through the recirculation valve and condenses the exhaust gas at a predefined temperature. A liquid ammonia separator separates the condensed liquid ammonia from the flue gas, which is vented to the atmosphere.

The present invention provides a simple and practical mechanism for controlling the amount of ammonia that escapes from the SCR to the atmosphere. The system deploys an additional condenser module to condense the exhaust gas containing the escaped ammonia when the amount of escaped ammonia exceeds a predefined threshold. Further, the present invention employs a liquid ammonia separator to separate the condensed liquid ammonia from the exhaust gas, which can be reused in the system as an AdBlue solution.

The above and other features of the embodiments will be apparent from the following detailed description of the embodiments will become more apparent when read in conjunction with the accompanying drawings. In the drawings, like reference numbers refer to like elements.

1 Figure 12 illustrates a block diagram of a system for controlling the emission of ammonia evolved from selective catalytic reduction (SCR) into the atmosphere.

In the following, reference is made in detail to the description of the present subject matter, one or more examples of which are shown in the figures. Each example is provided by way of explanation of the subject matter and not by way of limitation. Various changes and modifications which are obvious to one skilled in the art to which the invention pertains are deemed to be within the spirit, scope and contemplation of the invention.

The present invention discloses systems for controlling the emission of ammonia escaped by selective catalytic reduction (SCR) into the atmosphere, the system comprising an SCR for reducing the amount of NO _x emission in the exhaust gas. A pair of ammonia sensors detect the presence of ammonia in the exhaust gas downstream of the SCR, with an electronically actuated recirculation valve being actuated when the amount of ammonia in the exhaust gas detected by the first ammonia sensor is greater than a predefined threshold. Further, a condenser module receives the exhaust gas through the recirculation valve and condenses the exhaust gas at a predefined temperature. A liquid ammonia separator separates the condensed liquid ammonia from the flue gas, which is vented to the atmosphere.

1 Figure 11 illustrates a block diagram of a system for controlling the emission of ammonia escaped by selective catalytic reduction (SCR) into the atmosphere, the system (100) including an SCR (101) for reducing the amount of _NOx emission in the exhaust gas. The SCR (101) uses ammonia for the chemical reduction of _NOx emissions to provide a predefined amount of nitrogen, water and carbon dioxide. Further, a pair of ammonia sensors (102a, 102b) detect the presence of ammonia in the exhaust gas downstream of the SCR (101), with an electronically actuated recirculation valve (103) being actuated by the vehicle's electronic control unit (ECU) when the signal from the first ammonia sensor (102a) detected amount of ammonia in the exhaust is greater than a predefined threshold. The ECU is pre-programmed with a predefined threshold that indicates the maximum allowable limit for the amount of ammonia present in the exhaust.

The system (100) further comprises a condenser module (104) for receiving the exhaust gas containing a predefined amount of ammonia through the recirculation valve (103), the condenser module (104) condensing the exhaust gas at a predefined temperature. The condensate obtained at the outlet of the condenser module (104) is transferred to a liquid ammonia separator (105) which separates the condensed liquid ammonia from the flue gas. The amount of ammonia in the exhaust gas at the exit of the liquid ammonia separator (105) is detected by the second ammonia sensor (102b), whereupon the exhaust gas is discharged into the atmosphere.

The present invention provides a simple and practical mechanism for controlling the amount of ammonia that escapes from the SCR (101) to the atmosphere. The system (100) deploys an additional condenser module (104) to condense the exhaust gas containing the escaped ammonia when the amount of escaped ammonia exceeds a predefined threshold. Further, the present invention employs a liquid ammonia separator (105) to separate the condensed liquid ammonia from the exhaust gas, which can be reused in the system (100) as an AdBlue solution.

Although at least one exemplary embodiment has been presented in the foregoing detailed description, it should be understood that numerous variations exist.

Reference List

100

system

101

Selective Catalytic Reduction (SCR)

102a, 102b

Pair of ammonia sensors

103

recirculation valve

104

capacitor module

105

liquid ammonia separator

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• US 6871489 B2 [0005]
• US7320781B2 [0006]

Claims (4)

A system for controlling emission of ammonia evolved by selective catalytic reduction (SCR) into the atmosphere, the system (100) comprising: a. an SCR (101) for reducing the amount of _NOx emissions in a vehicle's exhaust, the SCR (101) employing ammonia to chemically reduce _NOx emissions to provide a predefined amount of nitrogen, water and carbon dioxide; b. a pair of ammonia sensors (102a, 102b) for detecting the presence of ammonia in the exhaust gas downstream of the SCR (101), an electronically actuated recirculation valve (103) being actuated when the amount of ammonia in the exhaust gas is greater than a predefined threshold; c. a condenser module (104) for receiving the exhaust gas containing a predefined amount of ammonia through the recirculation valve (103), the condenser module (104) condensing the exhaust gas at a predefined temperature; i.e. a liquid ammonia separator (105) for separating the condensed liquid ammonia from the exhaust gas, wherein the amount of ammonia in the exhaust gas at the exit of the liquid ammonia separator (105) is detected by the second ammonia sensor (102b), whereupon the exhaust gas is discharged into the atmosphere. system (100) after claim 1 wherein the vehicle's electronic control unit (ECU) is pre-programmed with a predefined threshold that indicates the maximum allowable limit for the amount of ammonia present in the exhaust gas. system (100) after claim 1 wherein the recirculation valve (103) is actuated by the vehicle's ECU when the amount of ammonia in the exhaust gas is greater than a predefined threshold. system (100) after claim 1 wherein the condensed liquid ammonia obtained at the outlet of the liquid ammonia separator (105) is reused as AdBlue solution in the aftertreatment system of the system (100).

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